Question

How can you tell what causes a food allergy?

Answer

The problem with food allergy is that it is one of the most controversial topics in medicine. It undoubtedly exists but because there have been some exaggerated claims which have not been supported by objective scientific observations, there may be a skeptical response from many doctors. What is meant by food allergy medically is an exaggerated reactivity of the immune system to an ingested antigen (foreign body). By contrast, food intolerance is the term used for all abnormal reproducible reactions to food in which the causative mechanism is unknown and is not immunological. The reactions to foods in these cases include irritant toxic pharmacological (drug-like) and metabolic (body chemistry) effects of foods, enzyme deficiency or even the release of substances produced by fermentation of food residues in the bowel. Some foods contain pharmacologically active substances that act directly, for instance on the blood vessels in sensitive subjects to produce migraine. Food additives can also upset people.

The suspected food causes gut related symptoms or can produce specific syndromes of food allergy such as coeliac disease, cow milk protein enteropathy (intestinal disease) and syndromes of food intolerance such as irritable bowel syndrome, lactose intolerance and miscellaneous syndrome such as migraine and headache, asthma and urticaria (allergic skin rash). The diagnosis depends on a very careful history and certainly not dismissing what the patient says. A thorough examination is probably also necessary to exclude other causes of the problems. Skin tests are positive in about 75% of people to foods such as nuts, eggs or fish. However these tests may not be useful in everybody and then there is a reliance on elimination diets and food challenges (controlled exposure to food suspected of causing the problem). This really needs to be done by carefully followed protocols, probably also using placebos and under medical supervision. It would seem therefore that if you wanted further advice and elucidation of your problem you need to go to an allergist who could provide you with the necessary tests and considered evaluation of them.

Links

• Food allergy